3D GaN Fins as a Versatile Platform for a‐Plane‐Based Devices

Hartmann, Jana; Nicolai, Lars; Margenfeld, Christoph; Spende, Hendrik; Ledig, Johannes; Zhou, Hao; Steib, Frederik; Jaros, Angelina; Avramescu, Adrian; Straßburg, Martin; Trampert, A.; Wehmann, H.-H.; Lugauer, H.‐J.; Voss, T.; Waag, A.

doi:10.1002/pssb.201800477

Cited by 7 publications

(14 citation statements)

References 41 publications

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“…The dark-spot contrast can be used to estimate the dislocation density on the fin sidewalls. 25 Averaging over several fins, a dislocation density of (6 ± 3) × 10 7 cm −2 is obtained for the AlGaN fins with an aluminum content of around 30% investigated in this study. This is a remarkably low value compared to that of conventional heteroepitaxial AlN-on-sapphire templates, which generally exceeds a threading dislocation density of 10 9 cm −2 .…”

Section: ■ Results and Discussionmentioning

confidence: 64%

“…23,24 The properties of GaN microfins have been discussed by Hartmann et al, and dislocation densities on the nonpolar a-plane sidewalls as low as (3 ± 2) × 10 5 cm −2 have been demonstrated. 25 A universal challenge for the approach of GaN/AlGaN core−shell microstructures that other researchers and our group have struggled with is the mitigation of cracking of the AlGaN shell layers which grow under increasingly tensile strain as the aluminum content is raised. 26,27 In our case, the use of a graded short-period superlattice (SPSL) allows for the growth of a mostly crackfree AlGaN shell that presents itself as an appropriate template for the growth of nonpolar a-plane AlGaN QWs emitting at the intersection of the UV-A and UV-B spectral regions (further information can be found in Supporting Information S1).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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AlGaN Microfins as Nonpolar UV Emitters Probed by Time-Resolved Cathodoluminescence

2022

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Despite the continuous technological progress and recent commercialization of UV light emitting diodes for sterilization and disinfection applications, the performance of solid-state UV emitters still lags far behind that of their InGaNbased counterparts, which emit in the visible blue−green spectrum. Both fundamental physical aspects and material quality restrictions have been discussed as origin of this striking difference. In this study, GaN/AlGaN core−shell microfins with a-plane sidewalls are proposed as a model system to demonstrate the efficiency potential of ultra-low-defect nonpolar UV emitters. Such structures are manufactured by bottom-up selective-area metalorganic vapor phase epitaxy of GaN microfin cores and further overgrowth of the AlGaN active region, employing a compositionally graded GaN/AlGaN short-period superlattice for strain management. Using this approach, mostly crack-free AlGaN quantum wells emitting around 321 nm could be realized with a threading dislocation density of as low as (6 ± 3) × 10 7 cm −2 . The carrier dynamics within the nonpolar AlGaN structures are studied by time-resolved cathodoluminescence spectroscopy, revealing fast radiative recombination lifetimes down to 0.6 ns and distinct signatures of carrier localization at low temperatures. Delayed carrier emission from localized states within the cladding is proposed to be a cause for anomalously high effective carrier lifetimes observed at temperatures below 80 K. By analyzing the characteristic temperature dependence of radiative and nonradiative recombination processes and fitting the lifetime data with an appropriate model across the whole temperature range, a room-temperature internal quantum efficiency of (40 ± 6) % is estimated for the studied sample. The findings corroborate the interest in nonpolar AlGaN structures as highly efficient UV emitters.

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Section: ■ Results and Discussionmentioning

confidence: 64%

Section: ■ Experimental Sectionmentioning

confidence: 99%

AlGaN Microfins as Nonpolar UV Emitters Probed by Time-Resolved Cathodoluminescence

2022

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“…The fabrication process started with etching the GaN film to generate a fin structure by reactive ion etching (RIE) with a Ni mask layer, which was photolithographically patterned by the step and repeat projection aligner for the submicrometer‐sized fins. Recent research showed the availability of the bottom‐up growth of a fin using selective area metal–organic vapor phase epitaxy . Afterward, tetramethylammonium hydroxide (TMAH) treatment at 85 °C for 50 min was used in this structure to make the sidewall of the fin smoother, as shown in Figure b .…”

Section: Methodsmentioning

confidence: 99%

A Study on the First‐Derivative Output Properties of GaN Static Induction Transistor with Submicrometer Fin Width

Chun

Malakoutian

et al. 2019

Physica Status Solidi (b)

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The first derivative of output curves of a Schottky-junction vertical channel GaN static induction transistor (SIT) with a submicrometer-sized fin is studied to understand its fundamental electrical properties. It is found that the derivative of output curves increases with the increase in drain voltage (V ds ) in ohmic region because of the raised potential minima in the channel, which is not seen in SITs with a relatively long fin width. The influence of the gate voltages (V gs ) and V ds on electric potential in the channel is demonstrated by evaluating the contribution of V gs and V ds , expressed through two coefficients α and β. The ratio of α to β increases up to 31.1 from 16.3 with decrease in the fin width from 0.9 to 0.5 μm, showing a higher dependency of the potential minima on V gs and the fin width. The voltage gain expressed by α/β is 14.9 dB for the GaN SIT with a fin width of 0.5 μm.

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“…Metal-Organic Vapor Phase Epitaxy (MOVPE) is one of the most popular deposition methods used in the mass production of compound semiconductors, especially the III-V group compounds, such as gallium nitride (GaN) or gallium arsenide (GaAs). This technique has gained popularity over the past few decades due to rapid amount of development-especially in the field of optoelectronics and power electronic devicesbased on these semiconductor materials [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the High Pressure MOVPE Upside-Down Reactor for GaN Growth

et al. 2021

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The present paper focuses on the high-pressure metal-organic vapor phase epitaxy (MOVPE) upside-down vertical reactor (where the inlet of cold gases is below a hot susceptor). This study aims to investigate thermo-kinetic phenomena taking place during the GaN (gallium nitride) growth process using trimethylgallium and ammonia at a pressure of above 2 bar. High pressure accelerates the growth process, but it results in poor thickness and quality in the obtained layers; hence, understanding the factors influencing non-uniformity is crucial. The present investigations have been conducted with the aid of ANSYS Fluent finite volume method commercial software. The obtained results confirm the possibility of increasing the growth rate by more than six times through increasing the pressure from 0.5 bar to 2.5 bar. The analysis shows which zones vortexes form in. Special attention should be paid to the transitional flow within the growth zone as well as the viewport. Furthermore, the normal reactor design cannot be used under the considered conditions, even for the lower pressure value of 0.5 bar, due to high turbulences.

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3D GaN Fins as a Versatile Platform for a‐Plane‐Based Devices

Cited by 7 publications

References 41 publications

AlGaN Microfins as Nonpolar UV Emitters Probed by Time-Resolved Cathodoluminescence

AlGaN Microfins as Nonpolar UV Emitters Probed by Time-Resolved Cathodoluminescence

A Study on the First‐Derivative Output Properties of GaN Static Induction Transistor with Submicrometer Fin Width

Numerical Analysis of the High Pressure MOVPE Upside-Down Reactor for GaN Growth

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